# Homework Help: Washing Machine revolution

1. Dec 3, 2007

### ~christina~

[SOLVED] Washing Machine revolution

1. The problem statement, all variables and given/known data

A tub of a washing machine goes into it's spin cycle , starting from rest and gaining angular speed steadily for 8.00s, at which time it is turning at 5.00rev/s. At this point the person doing the laundry opens the lid and a safety switch turns off the machine. The tub smoothly slows to a rest in 12.0s. Through how many revolutions does the tub turn while it is in motion?

2. Relevant equations

3. The attempt at a solution

I don't even know where to start but

I'm not sure....do they mean revolutions when the tub starts untill the person opens the lid and all the way till the machine goes and slows to a stop?

Is this 2 part question which I add the revolutions in the end when the person opens the lid to the begining when the washing machine starts?

Last edited: Dec 3, 2007
2. Dec 3, 2007

### Kurdt

Staff Emeritus
3. Dec 3, 2007

### DaveC426913

Shoot - another misleading title. I thought the day had come that they would finally rise up and vanquish their oppressors...

4. Dec 3, 2007

### ~christina~

:rofl: untill then they shall be tethered to the wall with a water pipe.

5. Dec 3, 2007

### ~christina~

Thanks Kurdt, I'll see what I can do from that page.

6. Dec 4, 2007

### rl.bhat

If you draw a graph of time vs angular velocity, area under the graph gives you the total revolution from start to end.

7. Dec 4, 2007

### Bill Foster

The equation for angular motion is analogous to that for linear motion

$$x=x_0+vt+\frac{1}{2}at^2$$

$$\phi=\phi_0+\omega t+\frac{1}{2}\alpha t^2$$

8. Dec 4, 2007

### ~christina~

Yes I actually used that to solve this problem but I just didn't post a follow up on it since I think I get it.

Thanks.